- Hatz CB-1-
Establishing Center of Gravity Range
by Randy Brooks, NX24B "Bratz" CB-1 S/N535
 Hatz CB-1 Biplane Home Page

The Hatz plans gives only the C.G. location as loaded. I established a C.G. Range for my Bratz CB-1 as follows:

The Clark "Y" airfoil is used on the Hatz with 50 inch chord. The center of pressure range is 18% Forward and 35% Rearward or +9.0 inches and +17.5 inches from leading edge. Reference used is Technical Manual T-400, Theory of Flight. I prefer to use 33% or +16.5 inches for aft center of pressure.

  • Datum --- Lower wing leading edge
  • Forward C.G. --- +9.0 inches - 12.65 inches equals -3.65 inches
  • Rearward C.G. --- +16.5 inches - 12.65 inches equals +3.85 inches

 

Procedure to Use
CLICK HERE TO REFER TO SKETCH


  1. Calculate wing areas of upper & lower wings and add together.

  2. Use lower wing leading edge as datum.

  3. Divide upper wing area by total wing area equals 55% (approx.) of total
    area.

  4. Multiply the stagger (23") by 55 % equals -12.65 inches which locates
    leading edge of the Mean Aerodynamic Chord (MAC) from lower wing leading edge (datum).

  5. Forward C.G. equals 18% x 50 inches equals 9 inches aft of leading edge of MAC.

  6. Rear C.G. equals 33% x 50 inches equals =16.5 inches aft of leading edge of MAC.

  7. Locate forward C.G. in reference to (datum) lower wing leading edge.
    9 inches - 12.65 inches equals -3.65 inches

  8. Locate Rearward C.G. in reference to (datum) lower wing leading edge.
    16.5 inches - 12.65 inches equals +3.85 inches



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